Several scholars suggest that he was likely the most important god in the Roman archaic pantheon: He was often invoked together with Iuppiter (Jupiter)(Zeus)

Numa in his regulation of the Roman calendar called the first month Januarius after Janus, at the time the highest divinity.

In general, Janus was the patron of concrete and abstract beginnings, such the religion and the Gods themselves, of the world and the human life, of new historical ages, economical enterprises.

According to Macrobius and Cicero, Janus and Jana are a pair of divinities, worshipped as the sun and moon, whence they were regarded as the highest of the gods, and received their sacrifices before all the others.

He was frequently used to symbolize change and transitions such as the progression of past to future, of one condition to another, of one vision to another, the growing up of young people, and of one universe to another. He was also known as the figure representing time because he could see into the past with one face and into the future with the other.

When Romulus and his men kidnapped the Sabine women, Janus caused a volcanic hot spring to erupt.